Rubber dust has been recycled in various forms since the early 1990s. It has been used in coating compositions, for example by addition to asphalt or coal tar for use on asphalt and concrete surfaces. One example of such use has been in rubberized emulsion aggregate slurry (REAS) in which crumb rubber is blended into an asphalt emulsion. REAS has been used in resurfacing of roads. It has, however, proved to be difficult to utilize high percentages of recycled rubber in these compositions because of difficulties in applying compositions containing more than abut 10% recycled rubber to surfaces to be coated.
In my prior U.S. Pat. No. 5,252,632 I described a low cost coating composition comprising light weight hollow glass spheres and a conductive phase.
In my U.S. Pat. No. 7,304,100 I described production of a coating composition by mixing a cellulosic thickener with a latex and glass bubbles.
In my copending U.S. patent application Ser. No. 12/433,981 I describe an aqueous coating composition comprising a mixture of recycled rubber particles, and particles at least one of glass or plastic particles, graphite particles and fluorinated resin particles such as polytetrafluoroethytlene and a suspension agent or resin.
Rubber is typically vulcanized using sulfur. However, other vulcanization agents, including peroxides urethane cross linkers and metal oxides have also been used. In the early days of the rubber industry in the mid Nineteenth Century basic oxides such as zinc oxide and lead oxide were also used. Today, zinc oxide is often used as a cross-linking accelerator in combination with sulfur. US Patent Publication 2009/0215963 mentions the use of potassium permanganate followed by hydrogen peroxide to produce a vulcanized rubber with hydroxy groups on its surface from a recycled vulcanized rubber that has previously been treated with boiling acetone to remove plasticizers. The product obtained is intended to be surface-grafted to a vinyl polymer.